VrayDirt in a bump slot

[Dmitriytn]

This issue is going along from one version into another.
Can that be fixed soon, please?

I've reported it while was in beta https://forums.chaosgroup.com/forum/...in-a-bump-slot
but it's still there and hasn't been fixed.

[hermit.crab]

Thanks for the report. The issue is already logged (internal bug-tracker id: VMAYA-5990). We'll see what we can do.

[hermit.crab]

Could you elaborate a bit on what exactly are you trying to achieve with the mentioned procedure? Maybe we could provide a workaround.

[Dmitriytn]

Basically let's say I'm using vraydirt with some vraybitmap inside the radius to create a mask for dust and dirt, I would like to use same mask in the bump slot of the dust layer so it looks like it has a little thickness.
Or the other way to use it is to mask out the edges to show some raw metal under the paint layer. Again I want to use same mask in the paint layer to give it a little bit of the thickness.

I would like to make a note, that this function been working fine in vray 3 and in vray next till somewhere around 28/11/2019. This is at least me first time saw it in the nightlies, but it mind was around earlier, so not sure.
Also this bug isn't in the GPU version, only CPU is affected.

[hermit.crab]

You may try using a VRayDistanceTex with a gradient through a VRayColor2Bump to get the dirt thickness. Another method might be to use the VRayCurvature as the diffuse of a material, bake to texture (diffuse) and use the output as a mask instead.

[Dmitriytn]

yeah, DistanceTex will work only in some scenarios, when you can split the geo into two pieces at least. But when it has to affect itself, it not gonna work.
Baking is another option yes, but it's a long workaround as well.

Finger crossed that this bug can be fixed soon, as it's a very very flexible way to do shading work, and doesn't require to bake anything.
I found it's quite critical when it comes to do shader work, for the same reason I found texturing objects in substance or mixer takes way longer than I can do inside 3ds max and vray procedurally.

[seandunderdale]

I always assumed it didn't work due to the order of rendering. For example, you cant use AO for displacement since the AO calculation is run after the displacement calculation. I assumed it was the same for bump. Should this actually work then?

[Dmitriytn]

seandunderdale mate, It's a great feature to have, and it has been working just fine.
Grant Warwick had as specific streams and tutorials about it. It was soooo good, but it's been broken for more then a year now.

You can try it yourself in GPU version, still works there.

[seandunderdale]

We were trying to create displaced stitch holes in car seat geo using procedurally placed spheres along a stitch edge to create AO dots, which we wanted to then use to drive the displacement. That didn't work so I think I gave up on using AO for anything more than procedural masking. I'll keep this bump option in mind though when it becomes available again.

[Dmitriytn]

I never used it with displacement, but bump did work 100%
I even do have some material presets which I created a long time ago and it had this sort of workflow.

[Dmitriytn]

It's sort of working, see the broken edges. This effect I want, just need to get rid of the wireframe

[vlado]

The VRayDirt texture is not intended to work inside a VRayColor2Bump node. I may be able to reduce the wireframes but the effect will likely not be what you want.

Best regards,
Vlado

[Dmitriytn]

finger crossed it'll work just fine like it does in gpu version.
Missed it so much.

[fixeighted]

Thanks for this - it inadvertently led me to using distance tex as material displacement for stitch holes, which although not perfect, works very well to add some detail.

[vlado]

So I have build for this, but it would be good for someone to test it; if you want to do that, please email me to vlado@chaosgroup.com with the 3ds Max or Maya version that you are using.

Best regards,
Vlado